-snip-
Thank you very much for your help, I have found the problem, and I will try my best to help others in the future!
Hmm, that's odd.
If that was the issue, you shouldn't be getting the "
method not found (code-32601)" error; instead, you should be getting 'help' for walletpassphrase command.
Anyways, goo that it's solved at the end although there are inconsistencies in this thread.